Field of the Invention
The present invention relates to a semiconductor device and a semiconductor module which can reduce power consumption in an environment in which a high voltage is applied and control output in accordance with a potential state with respect to the reference potential of the supply voltage.
Background Art
In inverter circuits or the like, two totem-pole-connected switching elements are driven by high-side and low-side control circuits respectively. Isolated power supplies need to be used for these high-side and low-side control circuits separately.
A control circuit that controls a single-phase inverter requires a total of three isolated power supplies: two high-side isolated power supplies and one low-side isolated power supply. Furthermore, a control circuit that controls a three-phase inverter requires three high-side isolated power supplies, and therefore requires a total of four isolated power supplies, resulting in a large-scale control circuit.
There is also a configuration which uses a bootstrap circuit for a power supply of the high-side control circuit and adopts one power supply for the control circuit that controls the three-phase inverter to reduce the number of power supplies. However, since the bootstrap circuit cannot operate for a period during which the high-side switching element is ON (a bootstrap capacitor is not charged), it is difficult to adapt the bootstrap circuit to a control scheme in which the ON period of the high-side switching element is extended.
Thus, a configuration using a bootstrap compensation circuit is proposed in order to sufficiently charge the bootstrap capacitor and at the same time simplify the circuit and reduce the size thereof (e.g., see Japanese Patent Laid-Open No. 2011-234430). In the bootstrap compensation circuit, its supply voltage floats relative to a reference potential and the bootstrap compensation circuit controls ON/OFF of an output circuit according to whether the supply voltage is high or low. More specifically, a voltage-dividing resistor circuit is provided which detects a potential with respect to a reference potential of the supply voltage. The output thereof is inputted to an inverter circuit or the like which is set to a predetermined threshold, H and L are defined as a potential state and the output circuit is driven in accordance therewith.